Correlation of cochlear pathology with ABR threshold shift and DPOAE level shift following exposure to low-frequency noise

Details

• Personal Author:
  Bohne BA ; Harding GW ; Snow D
• Description:
  ABR thresholds & DPOAE levels were determined before & 1-3 times after a 24-h exposure to a 0.5-kHz OBN at 95 dB SPL. At termination, the EP was recorded in the 1st turn & carbon tracer injected into the endolymphatic space (ES). After 45 min, the cochlea was fixed with OsO4, plastic-embedded & dissected as a flat preparation. Quantitative data on hair-cell losses were collected. Cytocochleograms were prepared with ABR threshold shifts (TS) & DPOAE level shifts (LS) overlaid. Based on the functional results, organ-of-Corti (OC) segments in the 2nd & 1st turns were sectioned at a radial angle for light & TEM study. Four chinchillas were terminated by 3 h post-exposure (0-d); two were terminated at 1 wk. At 0 d, the animals had a TTS of 20-60 dB over 0.5-10 kHz & a TLS of 10-50 dB over 2-10 kHz. EP averaged 84 mV, similar to controls. OHC loss ranged from 2.2-10.5% & 0.8-2.8% in the apical & basal halves of the OC, respectively. IHC loss was negligible throughout the OC. Viewed by phase contrast microscopy, most missing OHCs were found to have been replaced by immature phalangeal scars & cellular debris was seen in the ES & Nuel spaces. Most remaining hair cells had normal shapes & stereocilia arrays. Hair-cell loss & damage were insufficient to account for the TTS & TLS. Over the extent of the TTS & TLS, the nerve fibers & endings below the IHCs were not damaged, while the outer pillar bodies were either non-parallel or buckled. By 1 wk, the TS & LS had improved considerably; EP averaged mV. The pillars were buckled over a smaller linear distance in the OC that was aligned with the frequency range of the residual TS & LS. Immature scars were still visible in the reticular lamina but the amount of cellular debris was decreased. We conclude that in the chinchilla, the most consistent pathological correlates of noise-induced TTS & TLS are an accumulation of cellular debris in cochlear fluids & injury to supporting cells that uncouples the stereocilia from the tectorial membrane. [Description provided by NIOSH]
• Subjects:
  Animals Hearing Hearing Loss Hearing Loss, Noise-Induced Laboratories Noise Occupational Health Safety
• Keywords:
  Cell-damage Cellular-reactions Exposure-levels Hearing-disorders Hearing-loss Laboratory-animals Noise-exposure Noise-induced-hearing-loss
• ISSN:
  0742-3152
• Publisher:
  Association for Research in Otolaryngology
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  Louisiana ; Missouri ; New Jersey ; OSHA Region 2 ; OSHA Region 6 ; OSHA Region 7
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  28
• NIOSHTIC Number:
  nn:20041575
• Citation:
  Abstr Midwinter Res Meet Assoc Res Otolaryngol 2005 Feb; 28:202
• Editor(s):
  Santi PA
• Federal Fiscal Year:
  2005
• NORA Priority Area:
  Disease and Injury: Hearing Loss
• Performing Organization:
  Washington University, St. Louis
• Peer Reviewed:
  False
• Start Date:
  20000401
• Source Full Name:
  Abstracts of the 28th Midwinter Research Meeting of the Association for Research in Otolaryngology, Febuary 19-24, 2005, New Orleans, Louisiana
• End Date:
  20130914
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:c70a95eab6d20a0dde3d55f4d0d1661fb4a6fd03e32bc71f9bbe9b5e8190de49cb66323f0fa5b229eff5e12e417336731d2cdb8b3efeee56ea0887236023c31d
• Download URL:
  https://stacks.cdc.gov/view/cdc/194109/cdc_194109_DS1.pdf
• File Type:
  [PDF - 193.54 KB ]